Grounding device



Patented June 12, 1934 UNITED STATES PATENT OFFICE Application October 31, 1928, Serial No.

10 Claims.

This invention relates to an electrical ground connection and to devices known as driven grounds which are used for grounding station and line electrical apparatus, parts of which are to be kept at earth potential. It relates also to the treatment of the soil in the region of the ground rod.

The objects of the invention are (l) to provide a grounding device which serves also as a soil treating tool to increase the conductivity of the soil surrounding the ground rod; (2) to provide a method of treating soil to increase its conductivity and to put it in condition to maintain the increased conductivity over a considerable period of time; (3) to provide a grounding rod in which copper or similar material may be used to afi'ord good conductivity and resistance to corrosion, and which may be of lighter construction than usual but nevertheless capable of being driven into the ground; (4) to provide a simple, inexpensive and efficient grounding rod with improved provision for introducing periodically into the soil surrounding the rod a substance that materially increases the conductivity of the soil.

A preferred embodiment of the invention is described herein and is illustrated in the accompanying drawing.

In the drawing:

Figure 1 is a central vertical sectional view through a grounding device embodying the present invention showing the manner of its insertion into the ground;

Figure 2 is a view of the same device in elevation as it appears after being inserted into the ground;

Figure 3 is an enlarged sectional view of a detail, the cap.

Figure 4 is a view of a pressure extruder used with the device.

It is known that the resistance of the soil itself is the largest factor in the total resistance of a grounding connection. The soil within a foot of the rod causes in some instances as much as 80% of the total voltage drop through the ground connection. It is this region then whose resistance should be lowered if there is to be any substantial reduction of the total resistance. Other factors are the length of the rod, its diameter and the conductivity of the material of which it is made.

The length of the rod for effective use being determined by the depth of the permanent moisture level, it has been the custom to determine the diameter of the rod by a consideration of the strength necessary to withstand the force used to drive the rod into the soil. The diameter thus found to be necessary is frequently greater than is needed for efiicient conduction since it is now established that the area of contact between the earth and the rod is not a factor of great importance and may even be left out of consideration. The gain in conductivity in the rod itself due to a larger diameter is negligible since the resistance loss in the rod itself is a small part of the total resistance of the ground connection. The best material probably is copper as it resists corrosion and is a good conductor, but a rod of copper alone,

if of a size no greater than is needed to make the electrical connection, is not sufficiently strong to withstand the forces applied in driving the rod into the ground. Therefore, in order to be driv- 0 able, the rod must be considerably larger than is needed once it is in the ground, thus entailing undesirable expense.

Soil resistance may be greatly reduced by sprinkling the ground with a salt solution or by introducing a solution in other ways into the soil. The difficulty inherent in such treatment is the lack of permanence of its effect. A need has been recognized therefore of providing an effective way of treating the soil surrounding a grounding device, particularly the soil around the lower end of the rod, so that its conductivity will be increased, and so that the effect of the treatment will not disappear within a short time. Similarly, there has been a need for a simple, inexpensive, easily driven ground rod of high conductivity; or, more specifically, the need has existed of an improved, inexpensive, drivable copper rod.

The present invention is designed to meet both needs mentioned above. It provides a new method of soil treatment and a grounding device peculiarly adapted to that method and of such construction as to be easily drivable when made of copper or of a similar material. The construction of the rod will be described first.

A piece of hollow tubing 10, preferably of copper, is attached to a driving point 11 of steel or other drivable material by means of rivets, welding, crimping of the tubing or otherwise. The point has a boss 12 on its upper end around which the end of the hollow tubing is received and to which the tubing is snugly secured. The hollow tubing has a number of small holes 13 just above the steel point 11. The length of the tubing is such as to reach a permanent moisture level, bringing the holes 13 opposite moist soil, and its diameter may be an inch or less.

The upper end of the tubing 10 is threaded to receive a cap 14..

The cap is provided with a nipple having a check valve of any usual type opening inward. The nipple is threaded or fitted with any type of slidable connection making a pressure tight joint, being thus adapted to form a detachable connection with a grease gun or other pressure device.

A pressure device 17 is attached whenever desired to the nipple 15 to discharge into the hollow tubing a viscous mixture containing, as an ingredient, ordinary salt, copper sulphate, or other material which increases the conductivity of the soil. The other substance or substances making up the mixture should be such as to make it viscous and not readily soluble in water. By viscous is meant capable of flow through the soil under pressure but incapable of material flow through the soil iuiless under pressure. Ordinary lubricating grease containing the conductivity-increasing substance is satisfactory. Another satisfactory mixture is one containing a cementitious substance as well as the conductive and other substances. This may be forced into the soil while still plastic. It forms, when set, aconductive medium in the moist earth adjacent the end of the tubing. A suitable pressure device is the alemite grease gun used in lubricating systems for automobiles. Any other device may be used if it is capable of extruding the grease-like or viscous mixture under suitable pressure.

The device is installed and operated as follows. A solid drivin rod 16 is placed within the hollow tubing 10 and is rested on the boss 12 of the steel point 11 which registers with the interior of the tubing. The driving force is applied to the upper end of the solid rod and is transmitted directly to the boss 12 of the drivable joint, causing the tubing-to be drawn down to the desired depth without requiring the application of the driving force compressively to the hollow rod 11. The driving rod 16 is then removed and the cap is put in place on the end of the tubing. With the cap sealing the tubing, the pressure extruder is connected to the nipple and the viscous mixture containing the substance which increases soil conductivity is forced into the tubing and out through holes 13 into the soil adjacent the end of the rod.

By the delivery under pressure, the soil adjacent the end of the rod is impregnated with the mixture containing a substance which greatly increases the soil conductivity. It is to be noted that the region affected is that in which the greatest voltage drop occurs. The increase in conductivity under good conditions is as much as one hundred per cent under this method of treatment.

The substance so deposited, being contained in the viscous mixture which is not readily soluble under the normal soil conditions, is not quickly carried away but maintains the increased conductivity for a considerable time. The effect of such substances as ordinary salt and copper sulphate has been known but no such efficient way of treating the soil with them has come into use.

The device may be recharged when necessary by a maintenance man furnished with a portable grease gun or other pressure device for delivering the mixture to the rod. If any dirt works into the holes 13 in the rod, it will be pushed out by the pressure of the new supply.

The construction of the device may be varied in many respects while retaining the underlying thought of this invention. It is important that the tubing, of copper or similar material, be

drawn into the ground rather than pushed in. This can be accomplished even if the drivable member extends all the way through the tubing, thus forming an integral extension of the drivable point The tubing in such case is secured to the lower end of the rod, corresponding to the separate drivable point 11 illustrated here, and is secured thereto at other points as well, particularly at the top in order to form a sealing joint. The driving rod for this purpose preferably is non-circular, i. e., either polygonal or with a. re-entrant portion, to afford a how passage for the viscous mixture between it and the tubing. The grease-gun or other pressure device connection leads to the space between the inner driving rod and the tubing at a point below the top sealing joint between the tubing and the rod. The method of soil treatment is carried out as described above.

I claim 1. The method of decreasing the resistance of a grounding connection including a driven ground rod which consists in introducing under pressure into the soil in the region adjacent the lower end of the rod, a mixture containing as an ingredient a substance which increases the conductivity of the soil and as another ingredient a substance which takes a permanent set.

2. The method of decreasing the resistance of a grounding connection including a driven ground rod which consists in introducing under pressure through the rod and into the soil in the region adjacent the lower end of the rod, a mixture containing as an ingredient a substance which increases the conductivity of the soil and as another ingredient 3. The method of treating soil to increase its conductivity which consists in impregnating the soil with a viscous mixture containing as an ingredient a substance which increases soil conductivity.

4. The method of soil treatment which consists in introducing under pressure into the soil a substance not readily soluble under normal soil conditions and containing as an ingredient a cementitious substance.

s a substance which increases the conductivity of the soil.

5 The method of decreasing the resistance of a grounding connection including a driven ground rod which consists in introducing under pressure into the soil in the region adjacent the lower end of the rod, a viscous mixture containing as an ingredient a substance which increases the conductivity of the soil.

6. The method of decreasing the resistance of a grounding connection including a driven ground rod which consists in introducing under pressure through the rod and into the soil in the region adjacent the lower end of the rod, a viscous mixture containing as an ingredient a substance which increases the conductivity of the soil.

7. The method of making ground terminals, which is characterized by injecting into the natural cavities of the earth an electro-conductive plastic material adapted to be molded during the process of injection into a permanent body which makes intimate contact with the surrounding earth.

8. The method of making ground terminals, which is characterized by injecting under pressure beneath the surface of the earth an electroconductive plastic material which is adapted to fill and be molded into adjacent cavities and to form a permanent body of irregular shape in intimate contact with the surrounding earth.

9. The method of making ground terminals,

which is characterized by injecting from below the surface of the earth an electro-conductive plastic material under pressure, said material being adapted to flow into the natural cavities and seams of the earth and form a permanent body of large superficial area.

10. A ground terminal compri sing an upright 

